The Carpenter Snow Creek Mining District covers roughly 9,000 acres in the Little Belt Mountains of southern Cascade County, Montana. Around 96 abandoned mines dating to the 1880s left behind tailings, waste rock, and mine-influenced water. The site was added to the National Priorities List on September 13, 2001. Cleanup is organized into five operable units covering the Town of Neihart, mines and watershed areas, the Silver Dyke Mining Complex, Neihart Slope drainages, and fluvial deposits along Carpenter Creek and Belt Creek down to Monarch.
Lead, arsenic, cadmium, copper, zinc, thallium, and manganese contaminate soil, sediment, surface water, and groundwater across the site. More than 20 mine openings discharge water with low pH and high dissolved metals. Carpenter Creek has no fish and few aquatic insects because of this contamination. People can be exposed by eating, breathing, touching, or drinking contaminated materials. Human exposure is not currently under control, and groundwater migration has not been stabilized.
EPA is the lead cleanup agency, working with the Montana Department of Environmental Quality, the U.S. Forest Service, and the U.S. Army Corps of Engineers. EPA has conducted removal actions since 2004, including stabilizing slopes, improving erosion controls, and removing tailings. Continuous water quality monitoring has been in place since 2009. A Record of Decision for Operable Unit 1, the Town of Neihart area, was issued in April 2009. Remedial action for that unit began in 2023, with excavation of contaminated residential soils and roadway material underway and completion expected between December 2027 and February 2028. The Belt Creek Tailings pile will be excavated and moved to the Mackay Gulch repository. Feasibility studies for Operable Units 2 through 5 are ongoing, with cleanup decisions expected between March and May 2027. A combined remedial investigation for the Fluvial Deposits unit started in June 2024.
In response to an October 2025 Lead Directive, EPA recommends annual blood lead testing for children under 7 living near the site. Residents are advised to bring their own drinking water, avoid using stream water, clean dirt from clothes and gear before leaving the area, and avoid harvesting edible plants from floodplain areas.
Community members can attend public meetings for updates. A field season kickoff meeting is scheduled for Thursday, May 28, from 5 to 6 p.m. at the Monarch Neihart Community Center in Neihart, Montana. A fact sheet covering the 2025 field season is available online. Site documents, including the 2026 Community Involvement Plan and the 2025 Field Season Summary Fact Sheet, are on file at the EPA Superfund Records Center in Helena, Montana, at 10 West 15th Street, Suite 3200, open Monday through Friday from 8:00 a.m. to 4:30 p.m.
